New pthread_barrier algorithm to fulfill barrier destruction requirements.

The previous barrier implementation did not fulfill the POSIX requirements
for when a barrier can be destroyed.  Specifically, it was possible that
threads that haven't noticed yet that their round is complete still access
the barrier's memory, and that those accesses can happen after the barrier
has been legally destroyed.
The new algorithm does not have this issue, and it avoids using a lock
internally.

1 files changed, 9 insertions, 6 deletions

diff --git a/sysdeps/nptl/internaltypes.h b/sysdeps/nptl/internaltypes.h
index 74e848f74e..203c548550 100644
--- a/sysdeps/nptl/internaltypes.h
+++ b/sysdeps/nptl/internaltypes.h
@@ -92,15 +92,18 @@ struct pthread_rwlockattr
 };
 
 
-/* Barrier data structure.  */
+/* Barrier data structure.  See pthread_barrier_wait for a description
+   of how these fields are used.  */
 struct pthread_barrier
 {
-  unsigned int curr_event;
-  int lock;
-  unsigned int left;
-  unsigned int init_count;
-  int private;
+  unsigned int in;
+  unsigned int current_round;
+  unsigned int count;
+  int shared;
+  unsigned int out;
 };
+/* See pthread_barrier_wait for a description.  */
+#define BARRIER_IN_THRESHOLD (UINT_MAX/2)
 
 
 /* Barrier variable attribute data structure.  */